Method of removing surface protrusions from thin films

Abstract

A method for removing a surface protrusion projecting from a layer of a first material deposited on a surface of a substrate. In accordance with one embodiment of the invention, a layer of a second material is applied on the layer of first material. A sufficient quantity of the second material is removed to expose the surface protrusion. The first material exposed through the surface protrusion is then removed.

We claim:  
     
       1. A field emission display (FED) constructed from a process comprising: 
       depositing a conductive thin film layer on a substrate in which the thin film layer has at least one surface protrusion;  
       covering the thin film layer with an insulating sacrificial layer having a top surface;  
       using chemical-mechanical planarization to remove a portion of the sacrificial layer from the top surface until the sacrificial layer has a thickness D to thereby expose on the top surface all surface protrusions having a height of at least D;  
       etching the surface protrusions from the thin film layer through the exposed portions of any such protrusions to form void spaces at the location of the surface protrusions, the void spaces being present within the thin film layer and the sacrificial layer;  
       etching the sacrificial layer to remove the sacrificial layer from the thin film layer to expose an upper surface of the thin film layer having void spaces distributed therein;  
       constructing emitters on an upper surface of the thin film layer;  
       forming a layer of insulating material above the thin film layer;  
       forming an extraction grid on the layer of insulating material above the emitters; and  
       constructing a transparent screen above the extraction grid, the screen having an anode and a cathodoluminescent coating on the anode facing the extraction grid.  
     
     
       2. The field emission display of  claim 1  wherein etching the surface protrusions from the thin film layer through the exposed portions of any such protrusions comprises applying an etchant to each protrusion that selectively removes the material of the thin film layer to a greater degree than the material of the sacrificial layer. 
     
     
       3. The field emission display of  claim 1  wherein covering the thin film layer comprises applying the insulating sacrificial layer having a thickness making top surface of the thin film layer less than the height of any surface protrusion. 
     
     
       4. The field emission display of  claim 1  wherein covering the thin film layer with an insulating sacrificial layer comprises conformally covering the thin film layer with the sacrificial layer. 
     
     
       5. The field emission display of  claim 1  wherein depositing a conductive thin film layer comprises physical vapor deposition. 
     
     
       6. The field emission display of  claim 1  wherein etching the sacrificial layer to remove the sacrificial layer comprises isotropically etching the sacrificial layer. 
     
     
       7. A field emission display (FED) constructed from a process comprising: 
       depositing a conductive layer on a substrate in which the conductive layer has at least one surface protrusion;  
       covering the conductive layer with a sacrificial layer having a top surface;  
       removing a portion of the sacrificial layer from the top surface to expose at least some of any surface protrusion in the conductive layer,  
       removing any such exposed surface protrusions from the conductive layer through the exposed portions of the protrusions to form void spaces at the location of the surface protrusions, the void spaces being present within the conductive layer and the sacrificial layer;  
       removing the sacrificial layer from the conductive layer to expose the conductive layer having void spaces distributed therein;  
       constructing emitters on an upper surface of the conductive layer;  
       forming a layer of insulating material above the conductive layer;  
       forming an extraction grid on the layer of insulating material above the emitters; and  
       constructing a transparent screen above the extraction grid, the screen having an anode and a cathodoluminescent coating on the anode facing the extraction grid.  
     
     
       8. The field emission display of  claim 7  wherein depositing a conductive layer on a substrate in which the conductive layer may have at least one surface protrusion comprises physical vapor deposition. 
     
     
       9. The field emission display of  claim 7  wherein the conductive layer comprises chromium. 
     
     
       10. The field emission display of  claim 7  wherein covering the conductive layer with a sacrificial layer having a top surface comprises forming a layer of silicon dioxide on the conductive layer. 
     
     
       11. The field emission display of  claim 7  wherein removing a portion of the sacrificial layer from the top surface to expose at least some of any surface protrusions in the conductive layer comprises chemical mechanical planarization of the sacrificial layer. 
     
     
       12. The field emission display of  claim 7  wherein removing any such exposed surface protrusions from the conductive layer through the exposed portions of the protrusions comprises etching the conductive layer. 
     
     
       13. The field emission display of  claim 7  wherein removing the sacrificial layer from the conductive layer comprises mechanical planarization of the sacrificial layer. 
     
     
       14. A field emission display (FED) formed from a process comprising the steps of: 
       forming a conductive layer on a substrate, the conductive layer having at least one surface protrusion;  
       covering the conductive layer with a sacrificial layer having a top surface;  
       plagiarizing the top surface of the sacrificial layer until the sacrificial layer has a predetermined thickness of D to thereby expose on the top surface all surface protrusions having a height of at least D;  
       removing portions of the conductive layer through any such exposed portions of the conductive layer to remove all surface protrusions having the height of at least D and forming void spaces at the location of the surface protrusions, the void spaces being present within the conductive layer and the sacrificial layer;  
       removing the sacrificial layer from the conductive layer to expose the conductive layer having void spaces distributed therein;  
       constructing emitters on an upper surface of the conductive layer;  
       forming a layer of insulating material above the conductive layer;  
       forming an extraction grid on the layer of insulating material above the emitters; and  
       constructing a transparent screen above the extraction grid, the screen having an anode and a cathodoluminescent coating on the anode facing the extraction grid.  
     
     
       15. The field emission display of  claim 14  wherein the sacrificial layer comprises silicon dioxide. 
     
     
       16. The field emission display of  claim 14  wherein the step of planarizing the top surface of the sacrificial layer comprises the step of chemical-mechanical planarization (CMP) of the sacrificial layer. 
     
     
       17. The field emission display of  claim 14  wherein removing portions of the conductive layer comprises the step of performing an etch to selectively remove the surface protrusions while leaving the sacrificial layer in tact. 
     
     
       18. The field emission display of  claim 14  wherein the step of removing the sacrificial layer from the conductive layer comprises the step of chemical-mechanical planarization (CMP) to remove the sacrificial layer.